1. Field of the Invention
The present invention relates to 5-fluorouracil derivatives and, more particularly, to novel 1-carbamoyl-5-fluorouracils represented by the formula ##STR2## wherein R represents alkyl containing 3-8 carbon atoms, and to their use for tumor therapy.
2. Description of the Prior Art
At the present time, a relatively large number of chemical compounds are recognized for use in clinical therapy for tumors in humans. These anti-tumor agents can be classified into alkylating agents, anti-metabolites, antibiotic anti-tumor agents, hormones, etc. The precise clinical use made of them depends upon the particular kind of tumors, but most of them are employed for acute or chronic leukemia and malignant lymphoma and a few are effective on solid tumors such as adenocarcinoma. Representative of the latter type are 5-fluorouracil and its low toxic derivative 5-fluoro-1-(2-tetrahydrofuryl)-uracil, which are known to be effective on adenocarcinoma. Thus, 5-fluorouracil is well known to be an effective antimetabolite used as an agent for mammary gland or gastrointestinal cancer therapy for humans. However, due to its high toxicity, 5-fluorouracil is not considered a desirable anti-cancer agent and improvement has been recognized as necessary. On the other hand, 5-fluoro-1-(2-tetrahydrofuryl)uracil while of lesser toxicity is substantially inferior to 5-fluorouracil in anti-tumor activity and it has been desired to develop 5-fluorouracil derivatives which are as non-toxic as 5-fluoro-1-(2-tetrahydrofuryl)uracil but are substantially more effective antimetabolites.
In addition most anti-tumor agents, including 5-fluorouracil and 5-fluoro-1-(2-tetrahydrofuryl)uracil, are applied by intravenous administration, resulting in various therapeutical problems for both physicians and patients. Among the reasons these anti-tumor agents are not orally administered is that they are absorbed with difficulty through the stomach and cause intestinal damage as a side effect. Accordingly, it has been desired to develop novel anti-tumor agents which are suitable for oral administration and thus free of these problems.